(1) Field of the Invention
The present invention relates to a tracing system for tracing and displaying a transmission route between multiplexers in a transmission network in which a plurality of stations are connected by lines, each station accommodating one or a plurality of multiplexers.
In recent years, to facilitate effective maintenance work in transmission networks, centralized supervisor systems for centrally supervising transmission devices remotely provided in the transmission network are required. In this type of the centralized supervisor system, a large number of transmission devices in remote stations are effectively centrally supervised and faults simultaneously occurring in transmission devices are indicated route by route, the indication being used to estimate the point at which the real fault has occurred in the transmission network.
A transmission path is used as transmission means for transmitting signals between switching devices, and various types of devices such as multiplexers and transmission devices are coupled to the transmission route in a complex manner. Thus, if a fault occurs at a single point, the fault may affect other devices coupled to the line in which the fault has occurred. The tracing of connections of a line is effective in estimation of a route through which the fault is extended.
The present invention is applicable to a centralized supervisor system for centrally supervising a large number of transmission devices and for displaying supervision results on a screen.
(2) Description of the Related Art
Conventionally, in this type of transmission route tracing system, a route map indicating each transmission route between stations, a station map indicating transmission paths in each station, and a multiplexer map (MUX map) indicating paths in which multiplexers accommodated in each station are connected, are alternatively displayable on a graphic display unit (GD). Looking at the screen on the graphic display unit (GD), an operator traces a transmission route from a multiplexer to another multiplexer opposite to it. The switching (transition) between maps to be displayed on the graphic display (GD) is carried out via a selecting operation of a maintenance worker except for the transition from the MUX map.
This selecting operation is carried out by designating lines to which attention is directed. However, in a case where there are multiplexers connected to each other in a "back-to-back" formation to provide a station with a relay function, a channel number identifying the traced line is changed on the way from the multiplexer to the other multiplexer opposite to it. Thus, in this case, it is difficult for the maintenance worker to trace the connections of the line on the respective maps.